plone.app.theming including content from external site

This seems possible, but I'm missing something. I'm using plone.app.theming (diazo). I'm trying to pull in pages from a cold fusion site. I can get the first page to load using but the page then has urls that refer to more data pages. The urls are formatted like this "./undergraduates_classes_info.cfm?crse=001A&sectnum=A" (which Plone is more than happy to parse) I've tried a variety of permutations to this and I can't seem to get it to work.

 <xsl:param name="ExtUrl" select="'http://exeternalsite'" />
    <xsl:template match="a/@href[contains(.,'/undergraduates')]">
        <xsl:attribute name="href">
            <xsl:value-of select="concat($ExtUrl, .)" />
        </xsl:attribute>
 </xsl:template>

I also need to pass the url to the command so that i can get the actual data back.

Any help is appreciate -- and maybe I'm approaching this incorrectly?

Unless I am misunderstanding your question (always possible), I think you are misunderstanding p.a.theming. p.a.theming can include theme assets (e.g. templates, images) from a remote site, but it is not intended for nor really capable of proxying in content from a remote site.